We are studying the role of cell surface carbohydrate-binding components in intercellular adhesion in cellular slime molds, mouse teratocarcinoma stem cells, and baby hamster kidney (BHK) fibroblasts. In slime molds, evidence accumulated over the last several years, has established that cell surface galactose-binding lectins mediate cell-cell adhesion by recognizing complementary receptors on adjoining cells. Under the current grant, we have purified and characterized 3 distinct lectin forms from the species Polysphondylium pallidum. We have also identified a receptor activity (which antagonizes the P.pallidum lectins) in detergent extracts of membrane preparations. Using an affinity precipitation method, we have substantially purified this activity. For our future studies, we propose 1) to characterize the receptor biochemically; 2) to determine if it is present on the cell surface by immunocytochemical or surface labeling methods; 3) to determine if it is developmentally-regulated during the acquisition of cohesiveness by P.pallidum amoebae; and 4) to determine if isolated receptor or oligosaccharides derived from it interfere with cell adhesion. In our studies of teratocarcinoma stem cells and BHk fibroblasts, we have identified cell surface components that recognize mannose-rich oligosaccharides. These components are identified as mediators of rosette formation between the tissue culture cells and certain species of erythrocytes. In both systems, specific carbohydrates that antagonize these cell surface binding components also inhibit intercellular adhesion. We propose a series of experiments to purify and characterize the BHK and teratocarcinoma surface components. Using antibodies and a series of inhibitory carbohydrates, we will thoroughly investigate the role of these components in cell-cell adhesion. In teratocarcinoma cells, we will investigate possible changes in these components with differentiation of the stem cells. In fibroblasts, we will determine the role of the rosette-mediating component in density-dependent inhibition of growth and contact inhibition of movement.